PURPOSE: To prepare an ozone-modified carbon black suitable as an additive for coloring coatings, etc., by heating and drying a powdery carbon black, removing agglomerates and bringing it into contact with an ozone-contg. gas in a vibrational fluidized bed.

CONSTITUTION: An aerosol-like carbon black formed in a reaction oven 1 is water-cooled in a cooling tower 2 and a powdery carbon black is separated and collected by means of a bag filter 3 and introduced into an air classification machine to remove foreign matters and coarse particles. Then the solid and the gas are separated by means of a bag filter 8 to collect a powdery carbon black. This carbon black is fed in a drying machine 10 and, after it is dried at 100°C or higher, it is passed through a vibrating screen to remove carbon black agglomerates. Then the powdery carbon black is introduced on a screen 13 in a vibrational fluidized bed type ozone reactor 14 to bring it into contact with an ozone-contg. air and then, ozone is removed with dried air. It is thereby possible to prepare efficiently an ozone-modified carbon black with excellent characteristics as an additive for coloring of ink.